Most so-called biofuels are transesterification products of any of a variety of animal fats and vegetable oils. When the oil or fat is exposed to an alcohol (typically methanol) under appropriate catalytic conditions, the fatty acids can cleave from the glycerol radical and react with the alcohol to form fatty acid esters. The transesterification reaction significantly reduces the viscosity of the oil. For more information on the manufacture and properties of such biofuels, the interested reader is directed to any of a variety of overviews such as, e.g., M. Graboski et al., “Combustion of Fat and Vegetable Oil Derived Fuels in Diesel Engines,” Prog. Energy Combust. Sci., vol. 24, pp. 125-64 (1998, Elsevier).
Most biofuel is refined using a process employing large amounts of water to remove the strong bases that catalyze the transesterification process. The resulting wastewater, absent some type of neutralization, is quite caustic and can cause problems if discharged directly into municipal treatment systems. One refining process that avoids this concern is described in U.S. Patent Publ. No. 2010/0199549 (Harnar et al.), which eliminates the need for water washing of the raw fuel product.
Another concern for biofuel refiners is the glycerin (glycerol) byproduct. While a viable market for raw glycerin exists, the methanol used in most biodiesel refining processes complicates its use in many of the available applications, e.g., pharmaceuticals, personal care products and food additives. Perhaps not coincidentally, these are the applications where glycerin often commands the highest prices. In agricultural settings, glycerin finds use as a feed additive and as an emollient in, for example, teat dips.
A teat dip is an antimicrobial composition used to cleanse and sanitize the teat area before and after milking; bacteria including Staphylococcus aureus, Streptococcus agalactiae, Mycoplasma bovis, and Corynebacterium bovis are commonly encountered in dairy farming operations. Application of such a composition is a significant part of the recommended program to reduce or control mastitis. Teat dips must have antimicrobial properties, have low human toxicity (because the teat dip can enter into a dairy product during collection of milk) and have low environmental impact when discharged into the waste stream produced by the area in which dairy animals are milked, often referred to as a milking parlor.
Optimally, a teat dip will condition the teat tissue at the same time that it is providing its sanitizing effects. A typical emollient is glycerin, originating either as a byproduct of corn ethanol plants or from petroleum.
Teat dips commonly are distributed in pre-mixed form from warehousing and supply plants to dairy farms. The vast majority of commercial teat dips are based on iodine, sometimes provided free in solution but more commonly complexed with, e.g., polyvinylpyrrolidone (Povidone). Exemplary formulations typically include large amounts (e.g., 91-95% (by wt.)) water, small amounts of acid and/or base, 2-4% (by wt.) complexed iodine, and 2-4% (by wt.) glycerin; such formulations typically have a pH of 4-5 and can be modified through the addition of viscosity modifiers, surfactants, stabilizers, additional antimicrobials (e.g., chlorhexidine, quaternary ammonium, dodecyl benzene sulfonic acid, nisin, hydrogen peroxide, etc.), and the like. The amount of free iodine in these types of teat dips typically varies from ˜0.15 to 3%, with lesser amounts (e.g., 0.18%) becoming more common so as to reduce teat irritation and to lessen the risk of iodine residues in milk; processing plants have notified producers that iodine needs to be kept out of the milk stream because it causes problems with processing and yields.
Some products currently used as teat dips actually increase disease due to a combination of poor formulation (free iodine is not available in lethal doses) and how the teat dip is used, i.e., as a viscous liquid (film) that stays on the teat and udder after milking, thereby providing a medium to attract and retain bacteria-laden solids such as feces. To complicate matters, the glycerin emollient can act as a food source for any bacteria that is trapped in or on the viscous dip or its dried residue. Applying more teat dip prior to the next milking can merely trap the bacteria in the older, still present layer present on the udder and teat.